The present invention relates to thermoplastic or elastomer impregnated and lubricated wire ropes and more particularly to the blending of such lubricants with amorphous polypropylene to improve the bonding between the lubricant and the wire rope strands and between the lubricant and the impregnating thermoplastic.
Various methods of impregnating wire rope with different types of thermoplastic material are known to improve the fatigue life, to reduce wire contact stresses and to inhibit corrosion of the wire rope. Certain such methods are disclosed in U.S. Pat. No. 3,824,777. A limiting factor effecting the corrosion resistance of thermoplastic impregnated wire ropes is that during the impregnation process, the high temperatures involved lead to the partial migration of the lubricant in the rope from contact with the wire strands. Further, no effective bond between the lubricant and the impregnating thermoplastic has been observed. Accordingly, if minor external damage occurs to the rope coating in a relatively small area, it is possible for contaminating elements to enter through the opening in the thermoplastic and to be drawn along the length of the wires of the wound rope strands by capillary action. Such action has a tendency to increase the internal corrosion of the wire rope.
An important factor in the corrosion resistance of a lubricated, thermoplastic impregnated wire rope is to insure that the inner wire rope core and each outer strand have a good quality lubricant uniformly distributed therein to maintain fatigue resistance of the strand and core. Further, the lubricant should have a high degree of elasticity to accept the bending and stretching of the wire rope in service. The lubricant should have a high degree of resistance to migration from the strands at the elevated temperatures necessary to effect the thermoplastic impregnation of the wire rope. Additionally, it is desirable that the lubricant material possess the ability to bond to the thermoplastic material impregnated into the wire rope. Typically, such thermoplastics include polypropylene, polyurethane, polyethylene, nylon or tetrafluoroethylene.
Accordingly, it is an object of the present invention to provide a wire rope and a method for making the same which utilizes a lubricant containing compound having a good adhesion quality to the wire strands and further having the ability to be bonded to the thermoplastic in-filling material.